CN117229425B - Method for preparing high-purity hydroxypropyl methyl cellulose - Google Patents
Method for preparing high-purity hydroxypropyl methyl cellulose Download PDFInfo
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- 229920003088 hydroxypropyl methyl cellulose Polymers 0.000 title claims abstract description 80
- 235000010979 hydroxypropyl methyl cellulose Nutrition 0.000 title claims abstract description 80
- 239000001866 hydroxypropyl methyl cellulose Substances 0.000 title claims abstract description 78
- UFVKGYZPFZQRLF-UHFFFAOYSA-N hydroxypropyl methyl cellulose Chemical compound OC1C(O)C(OC)OC(CO)C1OC1C(O)C(O)C(OC2C(C(O)C(OC3C(C(O)C(O)C(CO)O3)O)C(CO)O2)O)C(CO)O1 UFVKGYZPFZQRLF-UHFFFAOYSA-N 0.000 title claims abstract description 78
- 238000000034 method Methods 0.000 title claims abstract description 24
- 239000001913 cellulose Substances 0.000 claims abstract description 82
- 229920002678 cellulose Polymers 0.000 claims abstract description 80
- 238000006243 chemical reaction Methods 0.000 claims abstract description 41
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 40
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims abstract description 29
- 239000003513 alkali Substances 0.000 claims abstract description 29
- 238000006266 etherification reaction Methods 0.000 claims abstract description 22
- 239000011259 mixed solution Substances 0.000 claims abstract description 14
- 239000003431 cross linking reagent Substances 0.000 claims abstract description 13
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 30
- 238000002156 mixing Methods 0.000 claims description 22
- 239000012670 alkaline solution Substances 0.000 claims description 20
- 229920000742 Cotton Polymers 0.000 claims description 19
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 18
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 18
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 18
- 238000010438 heat treatment Methods 0.000 claims description 18
- 238000003756 stirring Methods 0.000 claims description 18
- NEHMKBQYUWJMIP-UHFFFAOYSA-N chloromethane Chemical compound ClC NEHMKBQYUWJMIP-UHFFFAOYSA-N 0.000 claims description 16
- 238000005507 spraying Methods 0.000 claims description 15
- 239000002699 waste material Substances 0.000 claims description 15
- 238000004132 cross linking Methods 0.000 claims description 14
- 239000002904 solvent Substances 0.000 claims description 13
- 238000005406 washing Methods 0.000 claims description 13
- 238000001035 drying Methods 0.000 claims description 12
- 239000000243 solution Substances 0.000 claims description 12
- 239000004753 textile Substances 0.000 claims description 11
- SXRSQZLOMIGNAQ-UHFFFAOYSA-N Glutaraldehyde Chemical compound O=CCCCC=O SXRSQZLOMIGNAQ-UHFFFAOYSA-N 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 239000008399 tap water Substances 0.000 claims description 9
- 235000020679 tap water Nutrition 0.000 claims description 9
- GOOHAUXETOMSMM-UHFFFAOYSA-N Propylene oxide Chemical compound CC1CO1 GOOHAUXETOMSMM-UHFFFAOYSA-N 0.000 claims description 8
- 229920003086 cellulose ether Polymers 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 7
- 238000001704 evaporation Methods 0.000 claims description 6
- 239000008367 deionised water Substances 0.000 claims description 5
- 229910021641 deionized water Inorganic materials 0.000 claims description 5
- 239000000645 desinfectant Substances 0.000 claims description 5
- 239000004744 fabric Substances 0.000 claims description 5
- 239000007788 liquid Substances 0.000 claims description 5
- 238000004659 sterilization and disinfection Methods 0.000 claims description 5
- LEQAOMBKQFMDFZ-UHFFFAOYSA-N glyoxal Chemical compound O=CC=O LEQAOMBKQFMDFZ-UHFFFAOYSA-N 0.000 claims description 4
- 229940015043 glyoxal Drugs 0.000 claims description 2
- 239000007921 spray Substances 0.000 claims description 2
- 238000005265 energy consumption Methods 0.000 abstract description 12
- 230000008569 process Effects 0.000 abstract description 12
- 230000008961 swelling Effects 0.000 abstract description 11
- 238000001179 sorption measurement Methods 0.000 abstract description 9
- 238000005516 engineering process Methods 0.000 abstract description 8
- 230000015572 biosynthetic process Effects 0.000 abstract description 7
- 238000007670 refining Methods 0.000 abstract description 7
- 238000003786 synthesis reaction Methods 0.000 abstract description 6
- 238000002360 preparation method Methods 0.000 abstract description 5
- 238000012824 chemical production Methods 0.000 abstract description 2
- 230000002195 synergetic effect Effects 0.000 abstract description 2
- 125000001449 isopropyl group Chemical group [H]C([H])([H])C([H])(*)C([H])([H])[H] 0.000 abstract 1
- 238000000746 purification Methods 0.000 abstract 1
- 239000000047 product Substances 0.000 description 24
- 230000000052 comparative effect Effects 0.000 description 22
- 239000012467 final product Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 230000035484 reaction time Effects 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- 238000011010 flushing procedure Methods 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical compound C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 description 2
- 230000003113 alkalizing effect Effects 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 229920006184 cellulose methylcellulose Polymers 0.000 description 2
- 238000001027 hydrothermal synthesis Methods 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 238000002791 soaking Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 102000004190 Enzymes Human genes 0.000 description 1
- 108090000790 Enzymes Proteins 0.000 description 1
- 229920001131 Pulp (paper) Polymers 0.000 description 1
- 150000008044 alkali metal hydroxides Chemical class 0.000 description 1
- IZALUMVGBVKPJD-UHFFFAOYSA-N benzene-1,3-dicarbaldehyde Chemical compound O=CC1=CC=CC(C=O)=C1 IZALUMVGBVKPJD-UHFFFAOYSA-N 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000001804 emulsifying effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- -1 hydroxypropyl Chemical group 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000004060 metabolic process Effects 0.000 description 1
- 125000000956 methoxy group Chemical group [H]C([H])([H])O* 0.000 description 1
- 229920000609 methyl cellulose Polymers 0.000 description 1
- 229940050176 methyl chloride Drugs 0.000 description 1
- 239000001923 methylcellulose Substances 0.000 description 1
- 235000010981 methylcellulose Nutrition 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 239000012429 reaction media Substances 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Polysaccharides And Polysaccharide Derivatives (AREA)
Abstract
The invention belongs to the field of chemical production processes, and mainly relates to a method for preparing cellulose, in particular to a method for preparing high-purity hydroxypropyl methyl cellulose. The invention optimizes the preparation process of alkali cellulose and the purification technology of hydroxypropyl methyl cellulose, in particular, the invention provides that the isopropyl alcohol-N-N-dimethylacetamide-water mixed solution is used as a medium to prepare alkali cellulose, and the synergistic effect of the isopropyl alcohol and the N-N-dimethylacetamide increases the alkali adsorption amount of cellulose and the swelling degree of cellulose; on the other hand, the etherification reaction is carried out in a microwave reactor, the reaction process is quickened by utilizing the microwave technology, and the synthesis efficiency of the hydroxypropyl methyl cellulose is improved; in order to prepare the hydroxypropyl methylcellulose with higher purity with low energy consumption, the solubility of HPMC in cold water is reduced by means of the characteristic of a cross-linking agent in the refining process, the reaction energy consumption is greatly reduced, the energy is saved, and the preparation of the hydroxypropyl methylcellulose with high purity with low cost and low energy consumption is realized.
Description
Technical Field
The invention belongs to the field of chemical production processes, and mainly relates to a method for preparing cellulose, in particular to a method for preparing high-purity hydroxypropyl methyl cellulose.
Background
Hydroxypropyl methylcellulose (HPMC) belongs to the class of nonionic cellulose ethers and is a derivative of Methylcellulose (MC). Is prepared from cotton and wood through alkalizing, epoxy propane and chloromethane etherification, and has molecular structure of [ C ] 6 H 7 O 2 (OH) 3-m-n (OCH 3 ) m (OCH 2 CHOHCH 3 ) n ] x . HPMC has excellent thickening, emulsifying, suspending, film forming, protective colloid, water protecting, adhesion, enzyme resisting, metabolism inert and other performances, and can be dissolved in cold water, ethanol and acetone with the concentration below 70%, and meanwhile, different performance varieties and products can be prepared by adjusting the proportion of methoxy and hydroxypropyl in the HPMC, so that the HPMC can be widely used in various departments such as food, petroleum, industry and the like, and plays an important role in social and economic development.
The production processes of HPMC can be divided into two main categories: a gas phase process and a liquid phase process. The developed countries such as Europe and America mostly adopt a gas-phase method process, wood pulp is used as a raw material, alkalization and etherification are carried out in the same reaction equipment, the reaction temperature and pressure are automatically controlled, the single batch yield is high, the reaction time is short, the investment is large, and once the fault occurs, major accidents are easy to occur. The domestic production mainly adopts a liquid phase process, adopts refined cotton as a raw material, adopts binary mixed organic solvent for intermittent treatment in alkalization and etherification, and has low risk. In order to make cellulose absorb more alkali and better wet, a large amount of alkaline aqueous solution is required to be consumed, in addition, due to the characteristic that HPMC is soluble in cold water and insoluble in hot water, hot water at 90 ℃ is often required to be used for washing in a traditional refining section, CN 108623697B proposes a technical scheme that flaky or chipped pulp is contacted with alkali metal hydroxide solution to obtain alkali-containing cellulose, and hydroxypropyl methyl cellulose is produced, but the technology is required to use hot water at 80-90 ℃ for filtering and washing in the refining section, and the heat energy consumption is high. The preparation method effectively solves the problems, greatly reduces the reaction energy consumption, saves the energy, and achieves the purpose of preparing the high-purity hydroxypropyl methylcellulose with low cost and low energy consumption.
Disclosure of Invention
Aiming at the problems, the traditional production scheme is optimized, the isopropanol-N-dimethylacetamide-water mixed solution is used as a medium for alkalizing cellulose, the penetration effect on a cellulose crystallization area is improved by adding the isopropanol, the alkali adsorption amount of the cellulose is increased, and the swelling degree of the cellulose is effectively increased by adding the N-N-dimethylacetamide. In addition, in the etherification reaction, the traditional heating technology has slow reaction rate and higher heat consumption, and the microwave technology is adopted in the patent to carry out the etherification reaction in a microwave reactor, so that the synthesis rate is greatly increased; on the other hand, the cross-linking agent is introduced into the refining section, so that the solubility of HPMC in cold water is reduced, the requirement of directly using tap water for flushing is met, the energy consumption of the whole reaction is reduced, and the high-purity hydroxypropyl methylcellulose is prepared with low cost and low energy consumption. The preparation method of the high-purity hydroxypropyl methylcellulose comprises the following specific synthesis steps:
s1, washing 700-1000 g of waste cotton textiles, airing, and mixing 84 disinfectant with deionized water according to the following ratio of 1:1, and then mixing the waste cotton textiles according to a solid-to-liquid ratio of 1:10 is added into 84 disinfection mixed solution, stirred at 60 ℃ for 0.5 h, after the color of the mixture is removed, the mixture is washed with water, then cellulose is crushed by a crusher and passes through a 100-mesh sieve, and the superfine crushing is carried out, thus obtaining the treated cellulose; the waste cotton textiles are used as raw materials, so that waste materials are effectively utilized, energy consumption is reduced, and the sustainable development concept is met;
s2, taking 4-5L of 90% -95% isopropanol or N-propanol, 0.5L-1L of water, 1-2L of N-N-dimethylacetamide or pyridine, uniformly stirring after mixing, adding NaOH or KOH into the mixed solution to prepare 10% -40% alkaline solution, and heating to 10-40 ℃; the alkaline solution is then treated with an alkaline solution: cellulose produced in step S1 = 1: spraying the crushed cellulose in the step S1 for 2-6 hours while stirring by a spray pipe according to the mass ratio of 4-6 to finish alkalization of the cellulose; the step mainly aims to effectively wet and expand cellulose, and when the cellulose and sodium hydroxide are subjected to complete reaction, the hydrogen bond between cellulose molecular chains is weakened, and hydroxyl groups are activated, so that the chemical activity of the cellulose is changed, and various cellulose derivatives can be generated; however, in the cellulose alkalization process, if water is used alone as a solvent, the alkali adsorption amount is small, the uniformity of the prepared alkali cellulose is poor, the subsequent etherification reaction can be influenced, if excessive alkali solution is used for soaking, the hydrolysis of the cellulose can be caused, on the one hand, the isopropanol-N-N-dimethylacetamide-water mixed solution is used as a medium, on the other hand, the addition of the isopropanol can improve the permeation effect on a cellulose crystallization area, the adsorption alkali amount of the cellulose is increased, meanwhile, the existence of alcohol can ensure the disorder degree of the cellulose, and ensure that the alkali aqueous solution is more uniform; the addition of the N-N-dimethylacetamide can effectively increase the swelling degree of cellulose;
s3, adding the alkali cellulose obtained in the step S2 into 0.5-1L toluene solution, uniformly stirring, adding 300-600 g of chloromethane and epoxypropane, then placing into a microwave reaction oven, performing etherification reaction for 0.5-1 h at a reaction temperature of 60 ℃, and generating cellulose ether, wherein the step adopts a microwave reactor to rapidly complete the synthesis process in a short time, and compared with the traditional heating method, microwaves can accelerate the chain breakage of cellulose, so that the synthesis rate is greatly improved;
s4, carrying out steam heating on the product prepared in the step S3 to obtain crude hydroxypropyl methyl cellulose, wherein the heating temperature is about 120 ℃, and evaporating and recovering the solvent so as to recycle the solvent. Mixing the crude hydroxypropyl methylcellulose with acetic acid or citric acid to adjust the pH to 4-6, adding glutaraldehyde or glyoxal as a cross-linking agent to carry out a cross-linking reaction, and washing with tap water for 2 times after the reaction is finished to obtain high-purity hydroxypropyl methylcellulose; the crude hydroxypropyl methylcellulose obtained in the step has good water solubility due to a large number of hydroxyl groups in the molecular structure, and in the refining section in the prior art, hot water with the temperature of more than 90 ℃ is needed for flushing, so that the heat energy consumption is high;
and S5, drying the wet product of the high-purity hydroxypropyl methylcellulose obtained in the step S4, adjusting the pH value to 7-9 in the drying process to remove crosslinking, and finally entering a finished product pulverizer to obtain the high-purity hydroxypropyl methylcellulose.
Preferably: the waste cotton textile in the step S1 is waste cotton cloth.
Preferably: and in the step S1, the powder with the thickness of 0.2-0.4 mm is obtained after superfine grinding.
Preferably: the concentration of isopropanol used in step S2 was 90%.
Preferably: the alkali liquor proportion used in the step S2 is as follows: cellulose=1: 6.
preferably: raw materials in the step S3: methyl chloride: propylene oxide was 1:0.4 to 0.6:0.3 to 0.7.
Preferably: the power of the microwave reactor in the step S3 is 400W.
Preferably: and in the step S4, the pH value of the solution is adjusted to 5.
Preferably: the amount of the cross-linking agent used in the step S4 is 5-15% of that of the crude HPMC.
Compared with the prior art, the invention has the beneficial effects that:
1. the raw materials adopted by the invention are waste cotton textiles, the price is low, and the waste is utilized.
2. The preparation of the alkali cellulose is carried out in a spraying state, and is not a traditional alkaline water soaking method, so that the alkalization process of the cellulose can be effectively controlled, and the yield of the hydroxypropyl methyl cellulose is improved.
3. Compared with the traditional method which uses single water as a medium, the technology can ensure that the aqueous alkali solution is more uniform, has stronger permeation effect on a cellulose crystallization area, increases the alkali adsorption amount of cellulose, increases the swelling degree of cellulose and is beneficial to further etherification reaction.
4. The invention uses the microwave reactor to carry out etherification reaction, thereby accelerating the reaction rate and improving the efficiency of the whole reaction.
5. According to the invention, the cross-linking agent glutaraldehyde or iso-dialdehyde is added in the S4, so that the solubility of the hydroxypropyl methylcellulose in cold water is greatly reduced by virtue of the characteristics of the cross-linking agent, the property of self cold water dissolution and hot water insolubility can be overcome, tap water is directly utilized to wash products, the reaction energy consumption is reduced, and the energy is saved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a reaction scheme of the present invention.
Fig. 2 is a scan of the cellulose of example 1.
FIG. 3 is a scan of high purity hydroxypropyl methylcellulose synthesized in example 1.
FIG. 4 is a scan of the hydroxypropyl methylcellulose synthesized in comparative example 1.
FIG. 5 is a scan of hydroxypropyl methylcellulose synthesized in comparative example 2.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects to be solved by the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the present patent.
Example 1
S1, washing 700 g cotton cloth, airing, and mixing 84 disinfectant with deionized water according to the following ratio of 1:1, and then mixing the waste cotton textiles according to a solid-to-liquid ratio of 1:10 is added into 84 disinfection mixed solution, stirred at 60 ℃ for 0.5 h, washed with water after the color of the mixture is removed, and then the cellulose is crushed by a crusher and passes through a 100-mesh sieve for superfine crushing to obtain 0.3+/-0.1 mm powder, namely the treated cellulose;
s2, taking 90% isopropanol 4L, water 0.5L and N-N-dimethylacetamide 1L, uniformly stirring after mixing, then adding NaOH into the mixed solution to prepare 20% alkaline solution, and setting the temperature to 20 ℃; the alkaline solution is then treated with an alkaline solution: cellulose produced in step S1 = 1: spraying the crushed cellulose in the step S1 by a spraying pipe according to the mass ratio of 5, and spraying 4 h while stirring to finish alkalization of the cellulose;
s3, adding the alkali cellulose obtained in the step S2 into 0.80L toluene solution, uniformly stirring, adding 400g of chloromethane and 500g of propylene oxide, then placing into a microwave reaction furnace, performing etherification reaction 1h with microwave power of 400W, and controlling the reaction temperature at 60 ℃ to obtain cellulose ether;
s4, carrying out steam heating on the product prepared in the step S3 to obtain crude hydroxypropyl methyl cellulose, wherein the heating temperature is about 120 ℃, and evaporating and recovering the solvent so as to recycle the solvent. Mixing the crude hydroxypropyl methylcellulose with acetic acid or citric acid to adjust the pH to 4, adding glutaraldehyde as a cross-linking agent to carry out a cross-linking reaction, and washing with tap water for 2 times after the reaction is finished to obtain high-purity hydroxypropyl methylcellulose;
s5, drying the wet product of the high-purity hydroxypropyl methylcellulose obtained in the step S4, adjusting the pH value to 9 in the drying process to remove crosslinking, and finally entering a finished product pulverizer to obtain the final product of the high-purity hydroxypropyl methylcellulose.
Comparative example 2: high purity hydroxypropyl methylcellulose was obtained in the same manner as in example 1 except that the alkalization of cellulose was performed in S2 using 5.5. 5.5L of water configured as a 20% alkaline solution;
comparative example 2: high-purity hydroxypropyl methylcellulose was obtained in the same manner as in example 1, except that 90% isopropyl alcohol 4L and water 0.5L were mixed in S2 and stirred uniformly to prepare a 20% alkaline solution for alkalization of cellulose;
table 1 shows the adsorption amount of alkali to cellulose and the swelling degree of cellulose prepared in example 1 and comparative examples 1 and 2. The interaction of cellulose with alkali to form alkali cellulose can undergo a series of physical and chemical changes, and in the subsequent etherification reaction, the swelling, uniformity and the like of cellulose can affect the final product. It can be seen from table 1 that the material prepared in example 1 has a greater adsorption of alkali and at the same time has the greatest degree of swelling. In comparative example 1, in which water alone was used as the reaction medium for the alkaline water, the adsorption amount and swelling degree of the alkali were poor, and these had an effect on the final product properties. Fig. 2 and 3 are scans of cellulose and hydroxypropyl methylcellulose, respectively, of example 1. Compared with cellulose, the microcosmic appearance of the hydroxypropyl methyl cellulose has the advantages that the interlayer binding force of the cellulose after alkalization and etherification is weakened and is looser. The scans of the products of comparative example 1 (fig. 3) and comparative example 2 (fig. 4) showed a poor degree of swelling compared to the cellulose of example 1, which suggests that there is a synergistic effect between isopropyl alcohol and N-N dimethylacetamide and water, which together promote the alkalization process of the cellulose, ensure the amount of alkali adsorbed by the cellulose, and at the same time, ensure an excellent degree of swelling.
TABLE 1
| Sample of | Adsorption quantity of alkali (100 g cellulose) | Degree of swelling (%) |
| Example 1 | 12.5g ± 0.5g NaOH | 308±15 |
| Comparative example 1 | 7 g ± 0.3g NaOH | 104±23 |
| Comparative example 2 | 10 g ± 0.1g NaOH | 181±14 |
Example 2
S1, washing 700 g cotton cloth, airing, and mixing 84 disinfectant with deionized water according to the following ratio of 1:1, and then mixing the waste cotton textiles according to a solid-to-liquid ratio of 1:10 is added into 84 disinfection mixed solution, stirred at 60 ℃ for 0.5 h, washed with water after the color of the mixture is removed, and then the cellulose is crushed by a crusher and passes through a 100-mesh sieve for superfine crushing to obtain 0.3+/-0.1 mm powder, namely the treated cellulose;
s2, taking 90% isopropanol 4L, water 0.5L and N-N-dimethylacetamide 1L, uniformly stirring after mixing, then adding NaOH into the mixed solution to prepare 20% alkaline solution, and setting the temperature to 20 ℃; the alkaline solution is then treated with an alkaline solution: cellulose produced in step S1 = 1: spraying the crushed cellulose in the step S1 by a spraying pipe according to the mass ratio of 6, and spraying 6 h while stirring to finish alkalization of the cellulose;
s3, adding the alkali cellulose obtained in the step S2 into 0.80L toluene solution, uniformly stirring, adding 400g of chloromethane and 500g of propylene oxide, then placing into a microwave reaction furnace, performing etherification reaction 1h with microwave power of 400W, and controlling the reaction temperature at 60 ℃ to obtain cellulose ether;
s4, carrying out steam heating on the product prepared in the step S3 to obtain crude hydroxypropyl methyl cellulose, wherein the heating temperature is about 120 ℃, and evaporating and recovering the solvent so as to recycle the solvent. Mixing the crude hydroxypropyl methylcellulose with acetic acid or citric acid to adjust the pH to 4, adding glutaraldehyde as a cross-linking agent to carry out a cross-linking reaction, and washing with tap water for 2 times after the reaction is finished to obtain high-purity hydroxypropyl methylcellulose;
s5, drying the wet product of the high-purity hydroxypropyl methylcellulose obtained in the step S4, adjusting the pH value to 9 in the drying process to remove crosslinking, and finally entering a finished product pulverizer to obtain the final product of the high-purity hydroxypropyl methylcellulose.
Comparative example 3: high-purity hydroxypropyl methylcellulose was obtained in the same manner as in example 2, except that the etherification reaction in S3 was a hydrothermal process, the heating temperature was set to 100 ℃, and the reaction time was 3h.
In comparative example 3, the etherification reaction was performed by a hydrothermal method, the heating temperature was set to 100 ℃ and the reaction time was 3 hours, whereas the microwave method in example 2, the temperature was 60 ℃ and the reaction time was 1 hour, and the advantages of the microwave technology were that energy could be directly transferred to the reactants, improving the reaction efficiency, reducing the formation of by-products and facilitating the synthesis of the final product.
Example 3
S1, taking 700 g refined cotton, crushing by a crusher, sieving by a 100-mesh sieve, and performing ultra-fineness crushing to obtain 0.3+/-0.1 mm powder, namely treated cellulose;
s2, taking 90% isopropanol 4L, water 0.5L and N-N-dimethylacetamide 1L, uniformly stirring after mixing, then adding NaOH into the mixed solution to prepare 20% alkaline solution, and setting the temperature to 20 ℃; the alkaline solution is then treated with an alkaline solution: cellulose produced in step S1 = 1: spraying the crushed cellulose in the step S1 by a spraying pipe according to the mass ratio of 5, and spraying 4 h while stirring to finish alkalization of the cellulose;
s3, adding the alkali cellulose obtained in the step S2 into 0.80L toluene solution, uniformly stirring, adding 800g of chloromethane and 800g of propylene oxide, then placing into a microwave reaction furnace, performing etherification reaction 1h with microwave power of 400W, and controlling the reaction temperature at 60 ℃ to obtain cellulose ether;
s4, carrying out steam heating on the product prepared in the step S3 to obtain crude hydroxypropyl methyl cellulose, wherein the heating temperature is about 120 ℃, and evaporating and recovering the solvent so as to recycle the solvent. Mixing the crude hydroxypropyl methylcellulose with acetic acid or citric acid to adjust the pH to 4, adding glutaraldehyde as a cross-linking agent to carry out a cross-linking reaction, and washing with tap water for 2 times after the reaction is finished to obtain high-purity hydroxypropyl methylcellulose;
s5, drying the wet product of the high-purity hydroxypropyl methylcellulose obtained in the step S4, adjusting the pH value to 9 in the drying process to remove crosslinking, and finally entering a finished product pulverizer to obtain the final product of the high-purity hydroxypropyl methylcellulose.
Comparative example 4: high-purity hydroxypropyl methylcellulose was obtained in the same manner as in example 3 except that the etherification reaction time in S3 was 2h.
The reaction yield is generally used for describing the reaction efficiency, the higher the yield percentage is, the higher the efficiency is, the more the obtained products are, the yields of the example 3 and the comparative example 4 are respectively 86-89% and 87-90%, and compared with the example 3, the etherification time of the comparative example 4 is doubled, but the yield is not obviously increased, so that the etherification reaction can be completed within 1h under the addition of a microwave technology, and the reaction efficiency is greatly accelerated.
Examples
S1, washing 700 g cotton cloth, airing, and mixing 84 disinfectant with deionized water according to the following ratio of 1:1, and then mixing the waste cotton textiles according to a solid-to-liquid ratio of 1:10 is added into 84 disinfection mixed solution, stirred at 60 ℃ for 0.5 h, washed with water after the color of the mixture is removed, and then the cellulose is crushed by a crusher and passes through a 100-mesh sieve for superfine crushing to obtain 0.3+/-0.1 mm powder, namely the treated cellulose;
s2, taking 90% isopropanol 4L, mixing water 1L and N-N-dimethylacetamide 0.5L, uniformly stirring, adding NaOH into the mixed solution to prepare a 20% alkaline solution, and setting the temperature to be 20 ℃; the alkaline solution is then treated with an alkaline solution: cellulose produced in step S1 = 1: spraying the crushed cellulose in the step S1 by a spraying pipe according to the mass ratio of 5, and spraying 4 h while stirring to finish alkalization of the cellulose;
s3, adding the alkali cellulose obtained in the step S2 into 0.80L toluene solution, uniformly stirring, adding 400g of chloromethane and 500g of propylene oxide, then placing into a microwave reaction furnace, performing etherification reaction 1h with microwave power of 400W, and controlling the reaction temperature at 60 ℃ to obtain cellulose ether;
s4, carrying out steam heating on the product prepared in the step S3 to obtain crude hydroxypropyl methyl cellulose, wherein the heating temperature is about 120 ℃, and evaporating and recovering the solvent so as to recycle the solvent. Mixing the crude hydroxypropyl methylcellulose with acetic acid or citric acid to adjust the pH to 4, adding glutaraldehyde as a cross-linking agent to carry out a cross-linking reaction, and washing with tap water for 2 times after the reaction is finished to obtain high-purity hydroxypropyl methylcellulose;
s5, drying the wet product of the high-purity hydroxypropyl methylcellulose obtained in the step S4, adjusting the pH value to 9 in the drying process to remove crosslinking, and finally entering a finished product pulverizer to obtain the final product of the high-purity hydroxypropyl methylcellulose.
Comparative example 5: high purity hydroxypropyl methylcellulose was obtained in the same manner as in example 4, except that glutaraldehyde was not added in S4, and the crude hydroxypropyl methylcellulose was washed with hot water at 90 ℃.
Comparative example 6: high purity hydroxypropyl methylcellulose was obtained in the same manner as in example 4 except that iso-dialdehyde was added in S4, and the crude hydroxypropyl methylcellulose was washed with hot water at 90 ℃.
Compared with the example 4, the comparative example 5 has no cross-linking agent added in the refining section, and directly carries out refining treatment, in the flushing process, hot water at 90 ℃ is needed, but in the example 4, the heat energy consumption of the reaction is greatly reduced due to the cross-linking property of glutaraldehyde only by utilizing tap water; as can be seen in Table 2, the product purity of example 4 is higher than that of comparative example 6, indicating that glutaraldehyde is more suitable for cross-linking hydroxypropyl methylcellulose than isophthalaldehyde.
The purity of the product is generally divided into five grades of >95%,90% -95%, 85% -90%, 75% -85% and 65% -75% in China. The purity of hydroxypropyl methylcellulose refers to the percentage of hydroxypropyl methylcellulose contained in the product, i.e., the percentage of pure hydroxypropyl methylcellulose after the impurity content is subtracted from the final product. Table 2 shows the product purity comparisons of examples 1, 2, 3, 4 and comparative examples 2, 6.
TABLE 2
| Sample of | Example 1 | Example 2 | Example 3 | Example 4 | Comparative example 2 | Comparative example 6 |
| Purity of product (%) | 95.8±0.2 | 90.6±0.4 | 91.4±0.2 | 92.8±0.1 | 87.6±0.5 | 88.6±0.3 |
The foregoing examples merely illustrate specific embodiments of the invention, which are described in greater detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention.
Claims (7)
1. A method for preparing high-purity hydroxypropyl methylcellulose, which is characterized by comprising the following steps: the specific operation steps are as follows:
s1, washing 700-1000 g of waste cotton textiles, airing, and mixing 84 disinfectant with deionized water according to the following ratio of 1:1, and then mixing the waste cotton textiles according to a solid-to-liquid ratio of 1:10 is added into 84 disinfection mixed solution, stirred at 60 ℃ for 0.5 h, after the color of the mixture is removed, the mixture is washed with water, then cellulose is crushed by a crusher and passes through a 100-mesh sieve, and the superfine crushing is carried out, thus obtaining the treated cellulose;
s2, taking 4-5L of 90% -95% isopropanol, 0.5-1L of water and 1-2L of N-N-dimethylacetamide, uniformly stirring after mixing, adding NaOH or KOH into the mixed solution to prepare 10% -40% alkaline solution, and heating to 10-40 ℃; the alkaline solution is then treated with an alkaline solution: cellulose produced in step S1 = 1: spraying the crushed cellulose in the step S1 for 2-6 hours while stirring by a spray pipe according to the mass ratio of 4-6 to finish alkalization of the cellulose;
s3, adding the alkali cellulose obtained in the step S2 into 0.5-1L toluene solution, uniformly stirring, adding 300-600 g of chloromethane and propylene oxide, then placing into a microwave reaction oven, performing etherification reaction for 0.5-1 h at a reaction temperature of 60 ℃, and thus obtaining cellulose ether;
s4, carrying out steam heating on the product prepared in the step S3 to obtain crude hydroxypropyl methyl cellulose, wherein the heating temperature is 110-130 ℃, and evaporating and recovering the solvent so as to recycle the solvent; mixing the crude hydroxypropyl methylcellulose with acetic acid or citric acid to adjust the pH to 4-6, adding glutaraldehyde or glyoxal as a cross-linking agent to carry out a cross-linking reaction, and washing with tap water for 2 times after the reaction is finished to obtain high-purity hydroxypropyl methylcellulose;
and S5, drying the wet product of the high-purity hydroxypropyl methylcellulose obtained in the step S4, adjusting the pH value to 7-9 in the drying process to remove crosslinking, and finally entering a finished product pulverizer to obtain the final high-purity hydroxypropyl methylcellulose.
2. A process for preparing high purity hydroxypropyl methylcellulose according to claim 1, characterized in that: the waste cotton textile in the step S1 is waste cotton cloth.
3. A process for preparing high purity hydroxypropyl methylcellulose according to claim 1, characterized in that: the concentration of isopropanol used in step S2 was 90%.
4. A process for preparing high purity hydroxypropyl methylcellulose according to claim 3, characterized in that: the alkali liquor proportion used in the step S2 is as follows: cellulose=1: 6.
5. a process for preparing high purity hydroxypropyl methylcellulose according to claim 4, wherein: the power of the microwave reactor in the step S3 is 400W.
6. A process for preparing high purity hydroxypropyl methylcellulose according to claim 3, characterized in that: and in the step S4, the pH value of the solution is adjusted to 5.
7. A process for preparing high purity hydroxypropyl methylcellulose according to claim 4, wherein: the amount of the cross-linking agent used in the step S4 is 5-15% of that of the crude HPMC.
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| CN1569901A (en) * | 2004-04-30 | 2005-01-26 | 北京理工大学 | Azido dihydroxypropyl cellulose nitrate preparation method and synthesis |
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| CN114702601A (en) * | 2022-04-25 | 2022-07-05 | 石家庄市藁城区勇峰纤维素有限公司 | Production process of hydroxypropyl methyl cellulose and hydroxypropyl methyl cellulose |
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| CN107129540A (en) * | 2016-03-04 | 2017-09-05 | 浙江中维药业股份有限公司 | The Green production method of hydroxypropyl methylcellulose |
| CN114702601A (en) * | 2022-04-25 | 2022-07-05 | 石家庄市藁城区勇峰纤维素有限公司 | Production process of hydroxypropyl methyl cellulose and hydroxypropyl methyl cellulose |
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